Note: Descriptions are shown in the official language in which they were submitted.
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Stand-by instrument for aircraft
The invention relates to a stand-by instrument integrated onto the
instrument panel of an aircraft for displaying essential flight information in
the
case where primary systems develop a fault.
Conventionally, an aircraft is equipped with primary systems
allowing the determination and the display of information necessary for the
piloting thereof. The primary systems integrate notably inertial sensors and
pressure sensors linked to total and static pressure taps situated on the skin
of the aircraft. The primary signals delivered by the inertial sensors and the
pressure sensors are processed by an onboard computer which sends the
processed data to primary display systems. The primary display systems
comprise notably primary viewing screens integrated onto an instrument
panel of the aircraft. The primary viewing screens are doubled up, one group
of primary viewing screens being intended for the pilot and the other group
being intended for the copilot. Each group generally comprises a screen
presenting flight information such as the speed, the altitude and the attitude
of the aircraft and a screen presenting navigation information such as the
route to be followed and aircraft automatic piloting instructions.
Moreover, in order to be able to determine and explain the
circumstances and causes of an accident or of an incident on an aircraft, the
latter can be equipped with flight recorders, sometimes called "black boxes".
The installation of these flight recorders is compulsory in airliners. Two
types
of flight recorders currently exist, the first being a phonic recorder called
CVR, the acronym standing for the expression "Cockpit Voice Recorder", the
second being a recorder of flight parameters called FDR, the acronym
standing for the expression "Flight Data Recorder".
The phonic recorder serves to record radio communications,
voices and background noise in the flight deck, such as for example the
noise of the engines or alarms. These data are for example recorded in a
loop, over thirty to a hundred and twenty minutes. Four magnetic-tape tracks
can notably be used for recording these data, the tracks being for example
distributed in the following manner:
- radio-communications on tracks I and 4,
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- communications with the cabin crew on track 1,
- communications with the ground engineer on tracks 1, 2 and 4,
- background microphone on track 3.
The FDR serves for the recording, on the one hand, of parameters
of the aircraft, such as for example the operation of engines, of an automatic
pilot, the position of airfoils and flight controls, and on the other hand, of
flight
information displayed by the primary viewing screens, such as for example
the aircraft's speed, altitude and attitude. According to the aircraft's age
and
type, more than a thousand different parameters and items of flight
information may be recorded. In certain cases, it is possible to perform a
computer simulation of the flight on the basis of the parameters and flight
information recorded in the FDR. These data are for example recorded in a
loop over 25 hours, which is the regulatory minimum duration. The FDR is
linked to the aircraft's various computers and sensors by way of an
acquisition unit, known by the term "FDAU", the acronym standing for the
expression "Flight Data Acquisition Unit". The FDAU is notably charged with
selecting the parameters and the flight information to be recorded in the FDR
and to order them so as to send them to the FDR in a continuous frame. This
frame is formed of 12-bit words, sent at a rate of 64 to 1024 words per
second, depending on the aircraft type. The FDR then records this frame
directly in its memory. The content of the frame must satisfy requirements
defined by national and/or international regulations. In particular, the list
of
parameters and flight information to be recorded, as well as their recording
rate and the required accuracy are specified.
The flight recorders are designed so that the memories containing
the recorded data, namely notably the radio-communications, the
communications with the cabin crew, the flight deck noise, the parameters of
the aircraft and the flight information, are protected during an incident or
accident of the aircraft. In particular, the flight recorders must withstand
an
acceleration of 3400 g for 6.5 milliseconds, at a temperature of 1100 degrees
Celsius for one hour and at an immersion of at least 5000 meters of depth.
However, flight recorders are sometimes badly damaged. Not all the data
making it possible to determine the circumstances and causes of the incident
or accident of the aircraft are therefore always available for an
investigation
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of the incident or accident. In particular, in the case of complete
destruction
of the flight recorders, only the information recorded on the ground by air
traffic control can be used for the investigation. The recovery of the data is
also conditioned by their recording. A failure of the primary systems prevents
the recording in the FDR of the flight information and parameters of the
aircraft. Such is notably the case when a pressure tap, a sensor or the
onboard computer has failed. More generally, the existing solutions exhibit
the drawback of having only one source of information and of storing this
information in a single place of storage.
An aim of the invention is notably to alleviate all or some of the
aforesaid drawbacks. For this purpose, the subject of the invention is a
stand-by instrument that can be fitted to an instrument panel of an aircraft,
the stand-by instrument comprising means for calculating and displaying
stand-by flight information on the basis of stand-by signals provided by stand-
by equipment of the aircraft, characterized in that it comprises a memory and
means for recording during normal operation the stand-by flight information
and/or the stand-by signals in the memory of the stand-by instrument.
Stand-by instruments are used notably, but not exclusively, in
case of a fault with the primary systems. For this purpose, a stand-by
instrument presents information essential for piloting the aircraft, in
particular
the speed, the altitude and the attitude of the aircraft. This essential
information alone, called stand-by flight information, makes it possible to
pilot
the aircraft.
Previously, the information presented by stand-by instruments was
obtained and displayed by electromechanical instruments. The latter have
been replaced with electronic instruments, this having notably made it
possible to achieve advances in weight, size and reliability. Greater
flexibility
of use is moreover obtained since it is possible to add other information. In
particular, in addition to altitude, speed and attitude information, certain
stand-by instruments combine navigation information.
A stand-by instrument must also be autonomous and decorrelated
from the other onboard instruments. For this purpose, it integrates
equipment, for example sensors, making it possible to generate the
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information that it provides. Thus, it comprises pressure sensors linked to
total and static pressure taps situated on the skin of the aircraft. The
pressure
sensors make it possible notably to define the altitude and the speed of the
aircraft. It can also comprise an inertial unit, several temperature sensors
and
other types of sensors. The stand-by instrument's viewing screen can employ
liquid-crystal technology.
In addition to the information generated directly in the stand-by
instrument, the latter can receive information originating from other systems
fitted to the aircraft. This information travels for example over a serial bus
of
the aircraft, known by the term "ARINC", with reference to a digital data
transmission standard known as the ARINC standard (Aeronautical Radio
Incorporation). These data may for example indicate the heading of the
aircraft and are therefore displayed on the screen of the stand-by instrument.
The stand-by instrument can also send information to the outside,
notably to an automatic pilot of the aircraft. Indeed, since it itself
generates
some of the information that it displays, it can provide this information to
other systems integrated into the aircraft. In particular, the automatic pilot
needs reliable information. By way of example, the primary systems of an
aircraft comprise at least two inertia sensors. However, these sensors may
become faulty or deliver wrong information. In this case, the stand-by
instrument can make amends for the failed sensor and/or indicate which of
the two sensors is providing the right information. For an automatic pilot, it
is
therefore particularly important to have at least three items of information
for
one and the same parameter.
By construction, various instruments can be linked together but
there is always a segregation between the primary systems and the stand-by
instruments.
The invention has the main advantage that it makes it possible to
have available the flight information determined by the stand-by instrument
independently of the primary systems and flight recorders. In particular, it
makes it possible to have available the flight information determined by the
stand-by instrument even in the case of failure of one of the elements of the
primary systems or of the FDR. The invention also makes it possible to
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facilitate the determination of the circumstances and causes of the incident
or
accident of an aircraft by recording the flight information in a different
location
from the FDR, in this instance in a memory of the stand-by instrument. The
flight information can thus remain available even if the FDR is destroyed.
5
The invention will be better understood and other advantages will
become apparent on reading the detailed description of an embodiment
given by way of example, which description is given in relation to appended
drawings which represent:
- Figure 1, an instrument panel of an aircraft equipped with a
stand-by instrument;
- Figure 2, an example of information displayed by the stand-by
instrument;
- Figure 3, by a schematic, an exemplary embodiment of a
stand-by instrument;
- Figure 4, a memory of the stand-by instrument according to the
invention.
Figure 1 presents in a schematic manner an instrument panel 1 of
an aircraft, for example an airliner. The instrument panel 1 comprises means
for calculating and displaying primary flight information on the basis of
primary signals provided by primary equipment of the aircraft. For example, it
comprises two groups of viewing screens 2, 3. Each group comprises a
screen presenting notably primary flight information such as an altitude, a
speed and an attitude of the aircraft and a screen presenting navigation
information. The two groups 2, 3 are identical, one being reserved for a pilot
and the other for a copilot. These two groups form primary viewing screens.
The primary viewing screens are linked to an onboard computer processing
notably primary signals delivered by primary equipment so as to calculate the
primary flight information and the navigation information. The primary
equipment comprise notably inertial sensors and pressure sensors linked to
total and static pressure taps situated on the skin of the aircraft. The
assembly comprising the primary equipment, the onboard computer and the
primary viewing screens is called primary systems. A stand-by instrument 4
is placed between these two primary viewing groups 2, 3. Optionally, it is
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possible to provide several stand-by instruments. The stand-by instrument 4
of Figure 1 presents at least aircraft altitude, speed and attitude
information.
Figure 2 presents a stand-by instrument 4, of the electronic type,
fitted to an aircraft. The stand-by instrument 4 comprises a unit 10 and
display means. The display means comprise for example a liquid-crystal
screen 11 forming the front face of the stand-by instrument 4 and displaying
stand-by flight information, namely the attitude, the speed and the altitude
of
the aircraft. A first area 12 of the screen 11 presents the attitude of the
aircraft symbolized by its wings 13 with respect to a horizon line 14. A
second
area 15 displays the speed of the aircraft and a third area 16 displays the
altitude of the aircraft. In addition to these three essential items of
information, other information can be presented on one and the same page-
In the example of Figure 2, an area 17 is reserved for the information
regarding heading. By pressing a specific button 18, another page can be
displayed to present for example navigation information or other information.
In the case of a display defect of the primary viewing screens 2, 3, the
screen
11 of the stand-by instrument 4 is then used by the pilot and the copilot to
display the stand-by flight information.
Figure 3 illustrates a stand-by instrument 4 through a schematic
representation. The stand-by instrument 4 comprises stand-by equipment, for
example two pressure sensors 20, 21 linked to static 22 and total 23
pressure taps situated on the skin of the aircraft and an inertial sensor 24.
These various sensors 20, 21, 24 can be situated outside or inside (as
represented in Figure 3) the stand-by instrument 4. In all cases, the stand-by
equipment 20, 21, 22, 23, 24 is independent of the primary systems. The
pressure sensors 20, 21 make it possible to generate aircraft altitude and
speed information, while the inertial sensor 24 makes it possible to generate
aircraft attitude information. The information provided by these sensors 20,
21, 24 arrives at processing means 25, which utilize the stand-by signals
arising from the sensors 20, 21, 24 and optionally initialization parameters,
for example entered by the pilots, to generate the aircraft's altitude, speed
and attitude information. The processing means 25 can also receive
information provided by other systems via a bus 26, for example an ARINC
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bus. In particular, the processing means 25 can receive flight information and
navigation information originating from the primary systems 27. The
processing means 25 can also generate information for transmission to the
outside, for example via the bus 26, destined notably for the automatic pilot.
The stand-by flight information calculated by the processing means 25 and, if
appropriate, the information provided by the other systems is sent to display
means 28 so as to be displayed on the screen 11 of the stand-by instrument
4. The stand-by instrument 4 can also comprise a memory 29 managed by
memory management means 30. The memory 29 is for example internal to
the stand-by instrument 4. It makes it possible notably to store the
initialization parameters and the computer programs allowing the processing
of the stand-by signals originating from the sensors 20, 21, 24 and the
calculation of the stand-by flight information. The memory is read- and write-
accessible.
According to the invention, the stand-by instrument 4 can also
comprise means for recording during normal operation the stand-by flight
information. In particular, the memory 29 is also used to record during normal
operation the stand-by flight information generated by the stand-by
equipment 20, 21, 22, 23, 24 and the processing means 25. According to
another embodiment of the invention, another memory, physically distinct
from the memory 29, can also be used to record the stand-by flight
information. The stand-by flight information is recorded automatically
throughout the flight of the aircraft, without intervention from the pilot,
the
flight of the aircraft being understood as the period during which the stand-
by
instrument 4 or the primary systems 27 are switched on. The stand-by flight
information is for example recorded in such a way that it is possible to
redisplay it subsequently. Advantageously, this flight information corresponds
to the flight information used for the display on the screen 11 of the stand-
by
instrument 4. It is thus possible, after a flight, to recover and to analyze
the
stand-by flight information supplied to the pilot during the flight. In one
embodiment, the redisplay of the recorded stand-by flight information is done
on the screen 11 of the stand-by instrument 4, for example by way of the
memory management means 30, processing means 25 and display means
28. This embodiment exhibits the advantage of being able to analyze the
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stand-by flight information such as it was actually presented to the pilot
during the flight, the display that the pilot saw during the flight being so
to
speak regenerated. It is thus possible to detect a failure, if any, of the
stand-
by instrument 4, whether this failure is due to the processing means 25 or to
the display means 28.
In a particular embodiment, the memory 29 is an Electrically
Erasable Programmable Read Only Memory, called an EEPROM. This type
of memory allows an infinite number of readings of the content of the memory
and can be reprogrammed more than a million times. It exhibits notably the
advantage of not requiring any power supply to preserve the data stored in
memory. This type of memory is consequently particularly suited to the
storage of the initialization parameters and computer programs and in
particular the stand-by flight information, the aircraft's power supply means
generally being out of use in the case of an aircraft accident. The content of
this type of memory can also be recovered after removing the memory from
its support.
Advantageously, the memory 29 is a Flash Programmable Read
Only Memory called an FPROM, also more simply called a "flash memory".
The flash memory allows the modification of several memory spaces in a
single operation and is therefore characterized by very high read and write
speeds. It is of reduced dimensions, thereby making it possible to decrease
the risks of damage during an aircraft accident.
In a particular embodiment, the memory 29 is a flash memory with
NOT-OR logic, better known by the expression "NOR". This type of memory
possesses an addressing interface allowing random and fast access to any
location of the memory. It is consequently particularly suited to the storage
of
computer programs, the latter possibly being executed directly from the
memory.
Figure 4 illustrates the content of a part of a memory 29 of the
stand-by instrument 4 according to the invention. The stand-by instrument 4
can comprise means for recording at regular intervals the flight information
and means for managing the recording of the stand-by flight information in
the form of a rotating table. The content of the memory 29 is divided into two
areas, a first area being dedicated notably to the storage of the
initialization
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parameters and computer programs, and a second stand-by area 40 being
reserved for the storage of the stand-by flight information. As indicated
previously, the two areas can correspond to two distinct physical memories.
The content of the stand-by area 40 is structured in the form of a rotating
table. In this rotating table, a first row 41 contains all the stand-by flight
information taken at an instant to. The following row 42 contains the same
stand-by flight information taken at a following instant (to + r), z
representing
the time interval that has elapsed between the two recordings of the stand-by
flight information. In a particular embodiment, r is a time constant. The
following recording therefore occurs at an instant (to + 2.1-). Generally, the
stand-by flight information is recorded at the instants (to + i.z ), i being
an
integer lying between 0 and n, (n + 1) being the maximum number of rows
available to record the stand-by flight information. At the instant (to + (n +
1).r),
the stand-by flight information is again recorded in the first row 41, and so
on
and so forth. This rotating table principle makes it possible to record the
stand-by flight information sequentially and to keep in memory the stand-by
flight information of the last few hours of flight. The memory 29 can for
example be dimensioned so as to be able to retain the last one or the last 25
flight hours with an interval z of a few seconds or a few minutes. The
interval
r can for example be a second.
According to a particular embodiment, each item of stand-by flight
information, namely the altitude, the speed, the roll, the pitch and the yaw
of
the aircraft, is recorded in a column 43, 44, 45, 46, 47, 48, 49. Thus, each
item of stand-by flight information at a given instant is recorded in a
specific
memory location, the memory location being able to occupy one or more
physical elements of the memory 29 as a function of the size of the
information. According to another embodiment, the stand-by area 40 of the
memory 29 can record, with the stand-by flight information, the stand-by
signals originating from the sensors 20, 21, 24 or only these stand-by
signals.
The stand-by instrument 4 can be connected to the means for
calculating and displaying the primary flight information and comprise means
for recording during normal operation the primary flight information and/or
the
primary signals in the memory 29 of the stand-by instrument 4. In particular,
the stand-by area 40 of the memory 29 can record the primary flight
information and/or the primary signals originating from the primary systems
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27, such as a temperature, an air speed or an ascent speed. The Mach
number, an important parameter in the determination of lift, can also be
recorded in the memory 29. Advantageously, all the recorded information is
distributed in the stand-by area 40 of the memory 29 in the form of columns
5 43, 44, 45, 46, 47, 48, 49, each column containing one type of information.
The stand-by instrument 4 according to the invention makes it
possible to have available the stand-by flight information even in the case of
failure of the primary systems 27 or flight recorders during the flight of the
10 aircraft. The stand-by flight information also remains available in the
case of
complete destruction of the flight recorders in an accident. The stand-by
instrument 4 according to the invention also makes it possible to record the
flight information and the navigation information originating from the primary
systems. Furthermore, it exhibits the advantage of not requiring any
additional memory, but solely a modification of the computer program of the
stand-by instrument 4. The stand-by instrument 4 according to the invention
is therefore of economic design and facilitates the determination of the
circumstances and causes of an aircraft accident.
